package com.jwetherell.euler;

/**
 * Find the greatest product of five consecutive digits in the 1000-digit number.
 * 73167176531330624919225119674426574742355349194934 96983520312774506326239578318016984801869478851843
 * 85861560789112949495459501737958331952853208805511 12540698747158523863050715693290963295227443043557
 * 66896648950445244523161731856403098711121722383113 62229893423380308135336276614282806444486645238749
 * 30358907296290491560440772390713810515859307960866 70172427121883998797908792274921901699720888093776
 * 65727333001053367881220235421809751254540594752243 52584907711670556013604839586446706324415722155397
 * 53697817977846174064955149290862569321978468622482 83972241375657056057490261407972968652414535100474
 * 82166370484403199890008895243450658541227588666881 16427171479924442928230863465674813919123162824586
 * 17866458359124566529476545682848912883142607690042 24219022671055626321111109370544217506941658960408
 * 07198403850962455444362981230987879927244284909188 84580156166097919133875499200524063689912560717606
 * 05886116467109405077541002256983155200055935729725 71636269561882670428252483600823257530420752963450
 * http://projecteuler.net/problem=8
 * 
 * @author Justin Wetherell <phishman3579@gmail.com>
 */
public class Problem8 {

    public static final long solve(String number) {
        char[] chars = number.toCharArray();
        int b = 0;
        int e = 5;
        int max = 0;
        int product = 0;
        int length = chars.length;
        while (e < length) {
            product = product(b, e, chars);
            if (product > max) {
                max = product;
            }
            b++;
            e++;
        }
        return max;
    }

    private static final int product(int b, int e, char[] chars) {
        int result = 1;
        for (int i = b; i < e; i++) {
            result *= Character.getNumericValue(chars[i]);
        }
        return result;
    }

    public static final long ideal(String number) {
        char[] chars = number.toCharArray();
        int b = 0;
        int e = 5;
        int prevBegin = 0;
        int max = 0;
        int product = 0;
        int length = chars.length;
        for (int i = 0; e < length; i++) {
            if (i == 0) {
                product = product(b, e, chars);
            } else {
                prevBegin = Character.getNumericValue(chars[b - 1]);
                if (prevBegin <= 1) {
                    product = product(b, e, chars);
                } else {
                    int end = Character.getNumericValue(chars[e - 1]);
                    if (prevBegin != 0) product /= prevBegin;
                    product *= end;
                }
            }
            if (product > max) {
                max = product;
            }
            b++;
            e++;
            while (e < length) {
                int end = Character.getNumericValue(chars[e - 1]);
                if (end > 1) break;
                b++;
                e++;
            }
        }
        return max;
    }
}
